1. Field of the Invention
The present invention relates to a paper feeding cassette used to stock many sheets of paper which are fed to a machine.
2. Description of Related Art
A paper feeding cassette is used in an image forming apparatus, typically, a copying machine or a printer to feed paper such as a cut sheet and the like. There are many paper feeding apparatuses for image forming apparatuses that stock many sheets of paper before printing in advance and separately feed one sheet of paper after another from the topmost of the sheets piled up in a paper feeding cassette.
Some paper feeding cassettes are provided with a cursor. A cursor is movable along a rail disposed in a paper feeding cassette and contacts the sides of paper piled up in the paper feeding cassette to position the paper. Thus, the paper does not move from a given position and it becomes possible to carry out a stable paper feeding.
There are two types of cursor: one is a length-wise cursor that positions paper in the paper feeding direction and the other is a width-wise cursor that positions paper in the paper-width direction perpendicular to the paper feeding direction. These cursors are provided with lock means to lock the cursors in position that correspond to a paper size. Widely used is lock means that is comprised of a sawtooth rack and a engagement claw that engages with the rack.
However, if paper is loaded in a paper feeding cassette and a user tries to roughly move the paper feeding cassette in the paper-width direction, the bundle of paper is deviated relatively with respect to the paper feeding cassette under inertia and exceeds the limitation force of the cursor, and thus the lock piece is dislocated and the lock can be released. Accordingly, the paper moves in the paper-width direction together with the cursor. Consequently, it causes problems that the suitable paper feeding becomes impossible, and deviation of printed images or paper jam occurs.
To solve such problems, approaches have been proposed to prevent the unexpected movement of a lock piece that locks a width-wise cursor in position, and an example of such a paper feeding cassette is disclosed in JP-A-2005-231862.
In JP-A-2005-231862, a width-wise cursor that carries out the positioning of paper in the paper-width direction is disposed inside a cassette frame, under the width-wise cursor, a lock piece is rotatably supported in a plane intersecting at right angles with the paper-width direction, and the lock piece is energized in the lock direction by energizing means that is disposed near the pivotal shaft. An engagement hole is provided in the bottom surface of the width-wise cursor, a lock pin is provided on the upper surface of the lock piece, and the lock pin is inserted into the engagement hole to lock the width-wise cursor to prevent it from deviating in the paper-width direction. When a release rod disposed in the width-wise cursor is pushed down, the lock piece is moved to a lock release position, which is the technology disclosed in JP-A-2005-231862. With this technology, it is possible to prevent paper form deviating in the paper-width direction even if a user moves roughly the paper feeding cassette in the paper-width direction.
However, in the conventional technology described above, there are many constituting members such as a lock piece to hold a lock pin, energizing means, a release rod to release lock, etc. Besides, there has been a disadvantage that it takes a long time to assemble these constituting members with a paper feeding cassette.
In JP-U-1995-40646, provided is lock means that fixes the position of a width-wise cursor when a lid covers the upper surface of a cassette frame, and releases the width-wise cursor from the fixed position when the lid opens the upper surface of the cassette frame. However, because the lock means comprises a chevron-shaped protrusion in section and a recessed portion formed in the lid to engage with the protrusion, and because the lock means has a low reliability in its engagement, there has been a problem that the lock means comes out of the engagement if paper is loaded roughly.